Corrosion inhibitor



Patented uns ii, i

was

CORROSION IN,

Joseph R. Heard, In, Wyandotte, Mich, assignmto Wyandotte Chemicals Corporation, Wyandotte, Mich, a corporation ofi Michigan No Drawing. Application January 26, 1945,

Serial No. 574,819

7 Claims. I

The present invention relates to a corrosion inhibitor for use in anti-freeze mixtures used in the cooling systems of liquid-cooled internal combustion engines particularly those employed to propel automobiles and airplanes. The present application is a continuation-in-part of my prior application Serial No. 433,463 filed March 5, 1943.

It is well known that the metal parts in the cooling system of internal combustion engines comprise iron, copper, brass, solder and aluminum, in addition these metals are in electrical contact and consequently local electric cells are formed. Corrosion of these metal parts has occurred and attempts have been made to inhibit or to lessen the corrosion of the. metallic parts of such cooling systems by the use of corrosion inhibitors in the liquid employed as a cooling medium. of many types of corrosion inhibitors among which may be mentioned borax, ethanolamine, particularly triethanolamine, sulfonated oils, resinates, sodium nitrite either alone or mixed with other inhibitors, such as small amounts of maleic acid, picric acid, molybdates, tungstates, urea, naphthenates, etc. In German Patent No. 485,012 there i disclosed an anti-freeze mixture containing 25 parts glycol, 75 parts water and 0.2 part sodium hydroxide. It is suggested in this German patent that guanidine can be sub- 30 In the search for a satisfactory corrosion in- 40 hibitor or erosion inhibitor it must be borne in mind that the'inhibitor must be efi'icient not only at ordinary temperatures, such as those below 100 F. (37.7 C.) but also at elevated such as those at which the internal combustion en- 46 gine operates most efiiciently, for example, 160 to 180 F. (GO-822 0.). The inhibitor must prevent corrosion whether due to the corrosion of the metals of the cooling system, whether The prior art has suggested the use the engine to the cooling medium. A Anti-freeze solutions such as alcohols or glycols when used in internal combustion engine cooling systems without the addition of a satisfactory corrosion inhibitor cause severe corrosion of the metals comprising the system, particularly the iron and aluminum portions thereof.

It is theobject of this invention to provide a corrosion inhibitor which will retain its inhibitory efl'ect in suppressing or preventing corrosion throughout the normal life of the cooling liquor. 1

It is a further object of this invention to provide a. corrosion inhibitor which will not be materially changed in effectiveness by air over the normal lifeof the cooling liquid.

It is a further object of my invention to provide a corrosion inhibitor which is soluble in concentrated alcoholic solutions such as glycols or methanol and thus facilitating the compounding of the anti-freeze material for storage and shipment.

Broadly stated, the corrosion inhibitor clescribed hereinafter may be employed in any cooling system which is constructed of metal. The novel corrosion inhibitor may be employed in conjunction with the cooling medium used in the cooling systems of automobile and airplane engines, for example, and in the latter systems, les water or perhaps no water at all is employed in the cooling medium. The novel corrosion inthis corrosion is due simply to the cooling medium itself or to the electrolytic eflects or local couples that occur between the different metals .of the cooling system, or by the necessary rapid circulation of the cooling medium in order to hibitor may be used with any type of anti-freeze, such as methanol, ethanol, glycerol, ethylene glycol, propylene glycol, or a mixture of glycols. It has been found that guanidine carbonate is a highly eifective and satisfactory corrosion inhibitor for use in the cooling systems of internal combustion engines. When guanidine carbonate is added to one of the anti-freeze materials and diluted with water it has been shown that corrosion is prevented whether due to the corrosion of the metals of the cooling system as a result of the corrosive effect of the cooling medium, the electrolytic efiects that occur between the different metals or the necessary rapid circulation of the cooling medium.

The guanidine carbonate may be used in quantities of about 0.05% to about 2.0% of the weight of the concentrated anti-freeze component such as glycol. As a result of the presence of the uanidine carbonate the anti-freeze solution has an alkaline reaction of about pH 8 to pH 11. This-provides an alkaline reserve should acidity develop during prolonged usage of the cooling medium.

vorganiccompounlilesuohasiiisodiuln accuse 3- 'Whendesiredtheameuntcfguanldineearbonatemayhedeereasedandotheralhalineinencytofoamunderstrongagitatienaeoftenoecurs in the cooling systems.

compound. namely guanldine. roslon test results are set forth. wherein antifreeze solutions were made up containing 350 g. perliter of amixtureof2molsofethyleneglycol and 1 mol of propylene glycol, the balance being 650 g. of water. Test solutions were made up on thebasis of this mixture, each test solution containing guanidine carbonate, guanidine carbonat and disodium phosphate, and guanidine, respectively, and in the amounts as noted in Table I. Sets of metal test strips. including steel and aluminum which were assembled together in electrical contact and including other metals, namely brass, copper and solder, were then immersed in the continually stirred test solutions for a period of 1440 hours or 60 days and the amount of corrosion determined by the weight loss of the metal strips. The test period oi 60 days corresponds to about 2 seasons use of a commercial vehicle or six seasons use of a private pleasure car. The results of these corrosion tests on aluminum were as follows:

Team I Corrosion test results of mixed glycol-water solutions on aluminum in electrical contact with steel 4 tiensemnlo'insthenovel-gmnidineearbuate inhibitorareasiollows:

Partsbywlgli llinedethyleneandml neslycol (inthl.

mlend2mols.to-imol.l--.......- I. Water Ouanidine carbonate s lama 2 Parts by weight Denatured ethyl aleohoL eoe Water M Guanidine carbonate I Disodium hydrogen phosphate----.....-... 2.

Items 3 I 7 Parts by weight Mixed ethylene and P pylene glycol (in the Proportion of 2 mole. to 1 mol.) 360 Water 660 Guanldlne carbonate 3 Disodium hydrogen phosphate 2.5

' containing well-known types of prior art inhibitt 10 Percent in- Inhibitor (60 8:? at e: W carbonate MgJcm. Gunnldine mrbonate (6 g. p. l.)....--.. 0. 67 Guanidine carbonate (6 g. p. 1.2 and disodium hosphste (2.5 g. p. 0.91 as Guanidine 5 g. p. 1 2. l2 1 216 Guanidine 6 g. p. l.) days at 21 OJ. 2.04 204 1 Mixed col solution con l. guanidlne immediate] attacked when irfis iml ie ssd in solution under til; cleave conditions, as evidenced by formation oi bubbles and bubbling h on.

The corrosion tests of the mixed glycol solutions on steel followed'the' same general pattern as in the foregoing table, with the exception that the solution containing 5 g. per liter of guanidine carbonate together with 2.5 g. per liter of disodium phosphate showed better results than the solution containing the guanidine carbonate alone. For the purpose of comparison, the weight loss of the steel in the guanidine glycol mixture solution was 89% greater than the solution containing guanidine carbonate, and 154% greater 7 than the solution containing guanidine carbonate and disodium phosphate. All of the latter tests were, of course, run for thesame period of time, viz.: days at 69 C.

mg agents. The following table sets forth corrosion tests results upon the formulations of Examples l and 3 above. as well as two commercial anti-freeze compositions containing inhibiting agents. In this case, the metal strip sets were made up of iron, brass, aluminum and solder bolted together with brass bolts and nuts with brass spacer washers between the metal strips; and the size of strips, 1. e. their respective suriace areas, were in approximate proportion to that in which these metals would be present in an internal combustion engine cooling system. It suiilces to say that the iron or soft steel strip was present insubstantial excess over that of the remaining strips. The results of the corrosion tests so conducted as measured in the weight loss of the soft steel strips. were as follows:

Tam II Corrosion test results 0! mired glycol solution containing guanidine carbonate, and of cornmercially available glycol solutions containing other inhibiting agents Weight loss of Anti-traces solution 'g at M C MgJens I Formulation of Example 1 .m Formulation oi sample 004 Commercial anti-freeze solution ll- 31 Commercial anti-freeze solution #2 so scribed in conjunction with certain preferred embodiments, it is to be understood that variations and modifications thereof can be made as those skilled in the art will readily understand. Such variations and modifications are to be considered within the purview of the specification Illustrative examples of anti-freeze composi- 1s and the scope of the appended claims. Thus the term anti-freeze mixture as used hereinbefore and in the claims is to be understood as including not only th anti-freeze mixture when used in conjunction with water in cooling systems but also when the anti-freeze mixture is used per se as the cooling medium.

Equivalent modes of practicing my invention may be followed provided that they are within the scope and purview of the appended claims.

I, therefore, distinctly claim and particularly point out as my invention:

1. As a, new article of manufacture, an antifreeze mixture for use in coolin systems of liquid-cooled internal combustion engines in the presence of metals subject to electrolytic corrosion, said anti-freeze mixture consisting of water an organic water-soluble freezing point depressant and a small but effective amount of guanidine carbonate, said anti-freeze mixture having a pH value of about 8 to about 11.

2. As a new article of manufacture, an antifreeze mixture for use in cooling systems of liquid-cooled internal combustion engines in the presence of metals subject to electrolytic corrosion, said anti-freeze mixture consisting of water an organic water-soluble freezing point depressant and .05% to 2.0% by weight of guanidine carbonate on the basis of said'or'ganic freezing point depressant present.

3. As a new article of manufacture, an antifreeze mixture containing a corrosion inhibitor capable'of reducing substantially the corrosion of different metals in electrical contact forming at least a part of cooling systems of liquid-cooled internal combustion engines, said anti-freeze mixture consisting of about 350 parts by Wei ht of ethylene and propylene glycols in the proportion of 2 mols. to 1 mol., about 650 parts by weight .of water, about 3 parts by weight of guanidine carbonate and about 2 parts by weight of disodium hydrogen phosphate.

4. As a, new article of manufacture, an antifreeze mixture containing a corrosion inhibitor capable of reducing substantially the corrosion of different metals in electrical contact forming at least a part of cooling systems of liquid-cooled internal combustion engines, said anti-freeze mixture consistin of about 400 parts by weight ethyl alcohol, about 600 parts by weight water, about 5 parts by weight guanidine carbonate and about '2.5 parts by weight disodium hydrogen phosphate.

5. As a new article of manufacture/an antifreeze mixture containing a corrosion inhibitor capable of reducing substantially the corrosion of aluminum and ferrous metals in electrical contact with each other forming at least a part of cooling systems of liquid-cooled internal combustion engines, said anti-freeze mixture consisting of a mixture of ethylene and propylene glycol water and a small but efiective amount of guanidine carbonate, said anti-freeze mixture having a pH value of about 8 to about 11.

6. As a new article of manufacture, an antifreeze mixture containing a, corrosion inhibitor capable of reducin substantially the corrosion of aluminum and ferrous metals in electrical contact with each other forming at least a part of cooling systems of liquid-cooled internal combustion engines, said anti-freeze mixture consisting of a mixture of ethylene and propylene glycol water and .05% to 2.0% by weight of guanidine carbonate on the basis of said ethylene and propylene glycols present.

7. As a new article of manufacture, an antifreeze mixture containing a corrosion inhibitor capable of reducing substantially th corrosion of aluminum and ferrous metals in electrical contact with each other forming at least a part of cooling systems of liquid-cooled internal combustion engines, said anti-freeze mixture consisting of about 350 parts by weight of ethylene and propylene glycols in the proportion of 2 mols. to 1 mol., about 650 parts by weight of water, about 3 parts by weight of guanidine carbonate and about 2 parts by weight of disodium hydrogen phosphate.

"'UOSEPI-I R. IEARD, JR. 

